Convert Carat to Kilogram (ct → kg)
The carat equals 200 milligrams exactly and is the universal unit for gemstone and diamond weight in jewelry.
Carat to Kilogram Conversion Table
10 common values| Carat | Kilogram |
|---|---|
| 1 ct | 0.0002 kg |
| 5 ct | 0.001 kg |
| 10 ct | 0.002 kg |
| 25 ct | 0.005 kg |
| 50 ct | 0.01 kg |
| 100 ct | 0.02 kg |
| 250 ct | 0.05 kg |
| 500 ct | 0.1 kg |
| 1,000 ct | 0.2 kg |
| 5,000 ct | 1 kg |
How to Convert Carat to Kilogram Manually
Step by StepConverting carats to kilograms is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.
- 1Take your value in caratsStart with the number of carats (ct) you want to convert.
- 2Multiply by 0.0002The conversion factor from ct to kg is 0.0002. Multiply your value by this number.
- 3Read the result in kilogramsThe result is your value in kilograms (kg).
Formula
Multiply the value in carats by 0.0002. For the reverse direction, multiply by 5,000.
kg = ct × 0.0002ct = kg × 5,000Tips
Use these in everyday conversions- 1 carat = 200 mg = 0.2 g exactly since 1907.
- Carat (gem weight) and karat (gold purity, 24 K = pure) are different words with different meanings.
- A carat is divided into 100 points; a 0.25 ct diamond is called a "25-pointer".
Common Mistakes
Avoid these- Confusing carat (mass) with karat (gold purity).
- Assuming a 2-carat diamond is twice the physical size of a 1-carat — volume scales with cube root of mass.
- Using "karat" on gemstone certificates — international standard is "carat" spelled with a C.
About Carat and Kilogram
What is the Carat?
The carat equals exactly 200 milligrams (0.2 g) and is the universal unit for gemstone and diamond weight in the global jewelry industry. The word derives from the Greek 'keration' and the Arabic 'qīrāṭ,' both referring to carob seeds, which were once used as natural counterweights for weighing gems because they have remarkably uniform mass. The metric carat was standardized in 1907 at exactly 200 mg, replacing dozens of regional carat values that had varied between 188 and 213 mg. A 1-carat diamond is roughly 6.5 mm in diameter, and the famous Hope Diamond weighs 45.52 carats. The carat is distinct from the karat (with a 'k'), which measures gold purity (24-karat = 100% gold). It relates to the gram (5 ct = 1 g) and the milligram (200 mg = 1 ct). Gem dealers commonly use 'points' for fractions (100 points = 1 carat).
- Diamond and gemstone retail and valuation
- Jewellery manufacturing and design
- International gem certification (GIA, IGI)
A 1-carat diamond weighs 200 mg and is typically 6.5 mm across. The Hope Diamond is 45.52 carats (9.1 g).
What is the Kilogram?
The kilogram is the base SI unit of mass. Since May 2019, it has been defined by fixing the numerical value of Planck's constant to exactly 6.62607015 × 10⁻³⁴ joule-seconds — a major shift from the previous definition based on a physical platinum-iridium artifact (the International Prototype Kilogram or 'Le Grand K') stored at the BIPM near Paris since 1889. This redefinition links the kilogram to a fundamental constant of nature, making it reproducible by any sufficiently equipped laboratory. The kilogram is the global standard for body weight (most countries quote weight in kilograms), grocery sales, scientific measurements, and engineering. One liter of pure water at 4°C has a mass of almost exactly 1 kg — a coincidence designed into the original 1795 definition. The kilogram relates to the gram (1,000 g = 1 kg), the metric ton (1,000 kg = 1 t), and the pound (1 kg ≈ 2.205 lb).
- Human body weight in most of the world
- Grocery and retail food quantities in Europe
- Scientific and engineering mass measurements
A litre of water weighs 1 kg at 4 °C. An average adult weighs 60–90 kg. A standard bag of flour is 1 kg.